Method of separating isobutylene polymers from reaction mixtures



Aug. 19, 1952 H. G. HIPKIN ET AL 2,607,763

METHOD OF SEPARATING ISOBUTYLENE POLYMERS FROM REACTION MIXTURES Filed oct. 1e, 1947 SETTLN 'I'Am QEAeTwN vessel.

OLEPnJe Mtx-fuQ-a NLE-f bgg )ff Cltaor'oe Patented ug. 149, 1.952 y aeomss METHOD OF SEPARATING ISOBUTYLENE POLYMERS FROM REACTION llIIXTURES Howard G. Hipkin, Cambridge, Mass., and Harry B; Horwitz, Ottawa, Ontario, and Arthur G. Rogers, Sarnia, IOntario, Canada, assignors. to

Standard il Development ration of Delaware Company, a corpo- Application October 16, 194,7, Serial No. 780,210

2 Claims. (o1. 26o-'853) The present'invention relates to the art of producing hydrocarbon polymers of high molecular weight and rubber-like properties. The invention is specifically directed to the. handling of the polymerizate as it is withdrawn from the reactor in admixture with solvent at a low temperature. The invention will be fullyunderstood from the description and the drawing.

The drawing is a semi-diagrammatic View in sectional elevation of the apparatus for carrying out the process, illustrating the reaction vessel and the equipment required for preparing an aqueous slurry of the polymer from the reaction mixture of solvent and polymer.

In the production of synthetic resinous and rubber-like polymers by the low temperature technique, the reaction mixture containing polymer more or less completely dissolved in a low boilingv point solvent is withdrawn from the reactor at the extremely low temperature. of polymerization. The first object of the recovery processis to raise the temperature from the low temperature at which the polymerization takes place, to room temperature. The process of doing this must be carefully controlled in order to avoid fouling of equipment and agglomeration Aof polymer. It has been found that this can be accomplished best by discharging the mixture into a flowing stream of hot water so as to form an aqueous slurry of the polymer and cause evaporation of the solvent. In this condition the polymer is much less tacky, can be further handed without difficulty by dewatering, slabbing, drying-and finally packaging. The most difficult stage of handling is when the solventpolymer'mixture is directly withdrawn from the reactor.

Referring to the drawing, numeral I denotes a reaction vessel preferably in the form of an upright cylinder containingl a central draft tube 2. The tube is jacketed at 3 for cooling and in its lower end a propeller agitator 4 is placed driven by shaft 5 through the base of the vessel.

p' The sidewalls of the reactor are likewise jacketed bromide, boron fluoride and their equivalents,

dissolved in inert solvents of low boiling point and low freezing point.

The reactor I is kept full so that as the feed Many dlfferent polymers and copolymers may isadmitted, a part of the reaction bath is simultaneously withdrawn through a short pipe- I I and passed rapidly through a dispersing nozzle I2 by means of an atomizing stream of steam `admitted by pipe I3. The atomized mixture of solvent and polymer is discharged directly into a short, large diameter pipe I4 through which a relatively large volume of hot water is vcontinuously owing, entering at I5 andn discharging in to a vapor separator I l. Steam isadded to the short pipe I4 by means of a line Iandisalso sprayed directly into the separator by pipe I8, and in consequence the polymer mixture is rapidly heated to a temperature of say 140 .to 170 which, as will be understood, is well above the boiling point of the solvent. f f y 4.

Solvent vapors pass from the separator by a pipe I9 'to recovery equipment, not shown, and a suitable slurrying agent is added to the separator through a pipe 20, so that thev aqueous dispersion of the polymer which forms the liquid layer in separator I1 is in a stabilized condition. It is continually agitated by the stirrer 2|A and is drawn offvby a pipe 22 to a settling tank 23 wherein the dispersion is allowed to cream, the rubber polymer rising to the top on the aqu-Cous liquor forming the lower layer. This latter layer is recycled to the Vapor separator Il by a* pipe 24 and the concentrated aqueous dispersion forming the upper layer is removed by pipe 25 for the subsequent operations of dewatering, slabbing, drying, cutting and nally packaging, which steps neednot be illustrated since they are well known and form no part of the present invention.

be made by the low temperatureftechnique and .consequently can be handled by the present proybutene on the one hand with conjugated diolefins of 4 to'8 carbon atoms on the other, such as butadiene-1,3, isoprene, piperylene, and dimethyl butadiene. Y Suchv copolymerizations are accomplishedat 140to 160 F. vor thereabouts .in lowboiling hydrocarbon solvents. lsuch as butane vand pentane or mixtures such as the light naphthas of 4 to 7.,.carbon atoms. The solutions Lto permit` the solution to reach aconcentration ture of polymerization is from to 100 F. and l the proportion of styrene may be vfrom 20 to 70% by Weight. The polymerization is conducted in an alkyl halide such as methyl or ethyl chloride or other halides of 3 to 5 carbon atoms. VIn this case the catalyst is a Friedel-Crafts halide such as aluminum chloride, bromide or boron Vtriiiuoride dissolved in the solvent. The concentration of the resin may be as high as 30 to- 40% in -this case because the polymer makes afmuch less viscous solution than in the case of materials .withVV more rubbery characteristics.

While the above are examples, it will be ap-l preciated that they are merely illustrations of the types of materials to which the present process is adaptable, since in each case the polymerization occurs at low temperature, below atmospheric, and in the presence of a solvent, and it is required as a rst step to raise the temperature to normal or higher for recovery. In the present process it is extremely important to Vraise the temperature of the polymer solvent mixture as rapidly as possible from the reactor temperature level to a temperature above the boiling point-of the solvent thus giving the mixture the least possible opportunity to form deposits when it is in the most extremely tacky stage and in the presence of the solvent.

For the purpose of causing rapid heating of the polymer solvent mixture, it has been found that the most effective manner is to atomize and distribute the mixture through a large volume of flowing water at a temperature of 140-170 F. or thereabout. In this way the polymer inv its -most tacky state is kept out of contact with the Walls of the vessel and other equipment to the greatest degree possible and it is raised in temperature as rapidly Vas possible to eiect the vaporization of the solvent. The volume of Water does not appear to be critical but is conveniently from 5 to 30 times the volume of the cold mixture. In the manner described above, the deposits of polymer and the plugging of theapparatus are greatly reduced, but the lines should be smooth, short and with a minimum number ofV bends and pockets inviting accumulation,l as will be understood.

As an example thefollowing product" of an isobutene-isoprene rubbery polymei` will `be considered. The polymerization takes place at -'130 4 F. and a 4% solution of the rubber in a hydrocarbon solvent is obtained. This mixture was discharged at a rate of 28.9 gal/hr.V through a nozzle and atomized with steam using a .66#/ pound of the solution and into a stream of water so as to obtain a slurry containing 2% of rubber.

Zinc stearate was added as stabilizer. The operation was continuous, showed no difficulty by nozzle plugging or fouling, and was stopped after 8 hours after demonstration of complete success. The slurrywas fine, stable, uniform and practically free of lumps. In many instances it is desirable to add suitable slurrying and inhibiting agents to the hot water stream. These in some manner assist in the dispersion. Among these materials the best appear to be water-insoluble metal soaps such as zinc stearate or other soaps, or the soaps of alminum, magnesia, or calcium.

The present invention is not to be limited by any theory of the operation of thel polymerization or to any particular polymerizable ingredients dened, polymerization temperatures or the like, but only by the following claims in which it is desired to claim all novelty inherent in the invention.

We claim:

1. In a process for producing'high molecular Weight resinous to rubbery hydrocarbon polymers of isobutylene by polymerization at temperatures below 20 F., in the presence of a volatile inert solvent, by a Friedel-Crafts' polymerization catalyst, the improved method of recovering the polymers from the cold reaction mixture which comprises atomizing said cold mixture of polymer and solvent by passing it rapidly through an atomizing nozzle by means of an atomizing stream of steam, directly into a flowing stream of hot water having a volume 5 to 30 times the volume of the cold mixture of polymer and solvent, whereby the volatile solvent is vaporized, discharging the mixture into a vapor separation zone, removing solvent vapors from said zone, and withdrawing a slurry of solid polymer particles dispersed in water. Y

2. A process according to claim 1 applied to the production of a rubbery isobutene-isoprene copolymer at a temperature of about- F., and in which the cold mixture of polymer and solvent is atomized through a large volume of flowing water at a temperature of about to F. HOWARD G. HIPKIN.

HARRY B. HORWITZ. ARTHUR G. ROGERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

1. IN THE PROCESS FOR PRODUCING HIGH MOLECULAR WEIGHT RESINOUS TO RUBBERY HYDROCARBON POLYMERS OF ISOBUTYLENE BY POLYMERIZATION AT TEMPERATURES BELOW -20* F. IN THE PRESENCE OF A VOLATILE INERT SOLVENT, BY A FRIEDEL-CRAFTS POLYMERIZATION CATALYST, THE IMPROVED METHOD OF RECOVERING THE POLYMERS FROM THE COLD REACTION MIXTURE WHICH COMPRISES ATOMIZING SAID COLD MIXTURE OF POLYMER AND SOLVENT BY PASSING IT RAPIDLY THROUGH AN ATOMIZING NOZZLE BY MEANS OF AN ATOMIZING 